Simulation of convectiveconductiveradiative heat transfer in a cooling basin

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Simulation of convective-conductive-radiative
heat transfer in a cooling basin

• P. Vaitiekunas, V. Vaiis, D. Paliulis
• Dept of Environmental Protection, Vilnius
  Gediminas Technical University, Sauletekio al.
  11, LT-10223 Vilnius-40, Lithuania
• E-mail vaitiek_at_ap.vtu.lt, vaisisv_at_adm.vtu.lt,
  daipal_at_mail.ru
• 2006 11 28
• phoenics 3.6.1 VR (2004), PC Pentium 2

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Abstract

• The three-dimensional mathematical model of
  complex research of heat and mass transfer in
  water media was used. This allows examining the
  interaction of some transfer processes in the
  natural cooling basin (lake Drukiai) heat
  convection and conduction, direct and diffusive
  solar radiation, variable density of the water
  and heat transfer coefficient of the water-air
  interface. The combined effect of these natural
  and unnatural actions determines the heat amount
  that the basin is able to dissipate to the
  surrounding atmospheric media in thermal
  equilibrium (no change in the mean water
  temperature).
• This article presents a number of most
  widely used expressions for vertical and
  horizontal heat transfer coefficients.
  Suggestions are made that the mixing rate at the
  water surface is caused by natural space. There
  is analyzed case when there is no wind calm.
  Mean temperature profiles measured and predicted
  in the cooling pond, as well as on their time
  variation. A comparison experimental and
  numerical result showed a qualitative agreement.

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Content list

• 1. Objective of work
• 2. Description of phenomenon simulated
• 2.1 Qualitative
• 2.2 Mathematical
• 3. Presentation of results
• 4. Conclusions
• 5. Literature References
• 6. Non-standard nomenclature

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Objective of the work

• In order to qualify the cooling pond as an
  adequate thermal dissipater for the heat expelled
  by the station, will be necessary a composed
  analysis of the geographical, solar and water
  characteristics. The varying atmospheric and
  solar conditions make the basin to be a different
  characteristics dissipater everytime. Each one of
  the atmospheric or solar factors cannot determine
  by itself the dissipating capacity of the basin.
  All the elements are highly bound and must be
  treated simultaneously. The main objective is to
  establish these influences and to balance them
  with the heat coming from the nuclear power
  station. This analysis will provide us a base for
  establishing the capability of the basin to
  dissipate the heat completely or otherwise to
  calculate the net mean water temperature
  increase. The water temperature at the station
  intake will be the solution to a dynamic flowing
  and heat transfer problem that may be treated
  with PHOENICS CFD codes 1-3. We attempted to
  apply these codes in a simulation of two-phase
  mathematical model of the hydrothermal processes
  in a cooling pond, including the effects of
  three-dimensional (3D) structure features of the
  transport, power and direction of the wind,
  variable density of the water, heat conduction at
  the water-air interface, direct and diffuse solar
  radiation 4. In this paper is presented
  simulation of mass and heat transfer in a cooling
  basin according 2 but without wind blowing.

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Phenomenon simulated

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The lake Drukshiai with measured isoterms

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Fig 1. Difference grid (x.y.z41.17.9)
with contours of the lake Druksiai
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Equations solved

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Solar radiation
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Table 3. Numerical experiment results of basin
heat exchange

• The results table 3, row 1, presents experiment
  which assesses all heat exchange mechanisms by
  conductivity of water-atmosphere plus radiate
  exchange atmosphere-water and wateratmosphere,
  direct and diffuse solar radiation over the basin
  surface, in the row 2 ? temperatures without
  direct solar radiation effects, 3 ? without
  diffuse solar radiation effects, 4 ? without
  estimation of radiate heat exchange
  water-atmosphere, atmosphere-water. In row 5 are
  presented measured values 5, C0, and in 6-row ?
  percentage inclination predicted temperatures of
  row 1 from measured ones.
• yi
• 14 12 10 8 6 4
• 1 0C 27.77 27.96 27.56 26.12 26.08 26.20
• 2 0C 27.59 27.56 27.36 26.04 25.90 25.96
• 3 0C 27.73 27.91 27.51 26.10 26.03 26.15
• 4 0C 27.77 27.96 27.55 26.12 26.08 26.20
• 5 Exp., 0C 27.5 27.6 28.2 28.1 27.1 27.2
• 6 Res., 0.6 0.85 ?1.9 ?4.0 ?3.8 ?3.7

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Darbo ivada 1

• ISC-Aermod View nusistovejusio Gauso tipo dumu
  debesies modelis.

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4. Conclusions

• The code of elliptic equations was used to
  construct a numerical model of hydrothermal
  dynamics in lake Druksiai, in the region of the
  hot-water discharge and heat dissipation in the
  whole basin. The CFD codes were applied for the
  numerical solution of 3D mathematical model of
  the flow and heat transfer. The solutions can
  evaluate the effect of temperature-dependent
  water density, of water-air heat conduction, of
  water mixing and of the ground geometry.
• . Measurements and numerical simulations show a
  two-layer near field mixing structure, with the
  upper layer of the 2.5 m thickness.
• . An analysis of the numerical solutions for the
  hydrothermal processes in lake Druksiai, and
  their comparison with the test points suggest an
  influence of the water-air heat conductivity, of
  the variable density of water, of water mixing,
  and partially of the geometry of the shore-line
  on the results of simulation, which are
  qualitatively similar to the test points.

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5. Nomenclature
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6. Literature References

• 1. Montenegro H. S., Choucino M. A. (1994).
  Thermal dissipation in natural
• Basin The PHOENICS Journal of Computational Fluid
  Dynamics its applications. Vol.7, No. 3.
  P.1436.
• 2. Vaitiekunas P., Petkeviciene J., Katinas
  V. (1998). A Numerical simula-tion of
  three-dimensional hydrothermal Processes in a
  cooling pond. The PHOENICS Journal of
  Computational Fluid Dynamics its applications.
• Vol. 11,
  Nr. 3. P. 348-354.
• 3. Vaitiekunas P., Petkeviciene J., Katinas
  K. (2000). Numerical simulation of hydrothermal
  processes in lake Druksiai. Computational
  procedure. ISSN 0235-7208. Energetika. Nr.4. P.
  42-52.
• 4. Vaitiekunas P., Petkeviciene L. (2003).
  Two-phase numerical modeling of heat exchange in
  a natural basin. In Advances in Heat Transfer
  Engine-ering, Ed. B. Sunden and J. Vilemas. 4th
  Baltic Heat Transfer Conference, 25 27 August
  2003, Kaunas, p. 435-440.
• 5. Ecosystem of the cooling pond of the
  Ignalina NPP in the initial period of
• its operation. T. 10. D. 1. Vilnius.
  Akademija. 1992. 246 p.

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